JP4530320B2 - Microorganism immobilization carrier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microorganism-immobilized carrier used by attaching microorganisms to a surface when performing wastewater treatment biochemically.
[0002]
[Prior art]
One of the biological wastewater treatment methods is a method in which a microorganism-immobilized carrier to which microorganisms are attached flows in a tank, and organic matter and nitrogen are adsorbed and decomposed by microorganisms attached to the surface of the carrier. Is used. As this microorganism-immobilized carrier, hydrophilic gel, porous hollow resin, urethane foam and the like are used.
[0003]
Porous hollow resins are widely used because they are inexpensive and easy to mold. Examples of the porous hollow resin include polypropylene and polyethylene. Polypropylene is often foam-molded and used as a porous body in order to increase the adhesion amount of microorganisms.
However, since the microorganism-immobilized carrier made of a porous hollow resin has a high surface hydrophobicity and the surface is roughened by means of foam molding or the like for the purpose of facilitating adhesion of bacterial cells, the carrier is not suitable. Immediately after being put into the drainage tank, air bubbles adhered to the surface of the carrier and floated, so that it was difficult to flow when immersed in the drainage, and it took a long time to be able to perform good drainage treatment. .
[0004]
Therefore, many improvements for improving the hydrophilicity of the carrier surface have been proposed. For example, Japanese Patent Application Laid-Open No. 63-302994 discloses that a granular body made of an oxidizable thermoplastic resin is oxidized by contacting with a sulfochrome mixture (sulfuric acid, potassium dichromate and water) or a sulfonated mixture of fuming sulfuric acid. A method of hydrophilizing is disclosed. The carrier made of such oxidized particles improves the interaction with water and suppresses the floating phenomenon of the carrier and the condensation between the carrier bodies.
[0005]
Japanese Patent Application Laid-Open No. 58-198288 discloses a technique for improving the adhesion of microorganisms by forming irregularities on a carrier surface by etching the carrier surface with concentrated sulfuric acid.
[0006]
[Problems to be solved by the invention]
However, since the method for hydrophilizing the carrier surface described above uses a strong oxidizing agent such as concentrated sulfuric acid, there has been a problem that it is dangerous if handling is not performed with great care.
[0007]
Further, as disclosed in JP-A-58-198288, when the treatment is performed under severe conditions such that irregularities are formed on the surface, there is a concern that the carrier is excessively oxidized and a problem in durability occurs.
[0008]
In order to solve these problems, the present invention controls acid treatment conditions within an appropriate range, can be produced simply, inexpensively and safely, has good flowability immediately after use, and has excellent durability. It is an object of the present invention to provide a carrier.
[0009]
[Means for Solving the Problems]
That is, the gist of the present invention resides in a microorganism-immobilized carrier with improved fluidity obtained by treating a molded article containing an acid-modified thermoplastic resin and calcium carbonate with 0.1 N to 5 N hydrochloric acid.
[0010]
Moreover, since the fluidity | liquidity can be improved reliably when the said molded object is immersed in an acid for 0.1 to 10 hours, it is preferable.
Further, it is preferable that the acid is hydrochloric acid because it is excellent in handleability.
In addition, it is preferable that the thermoplastic resin contains an acid-modified thermoplastic resin because the initial fluidity is high, and it is more preferable that the thermoplastic resin further contains a propylene-maleic anhydride copolymer or an ethylene-methacrylic acid copolymer (ionomer resin). preferable.
Moreover, it is preferable that the content of the acid-modified thermoplastic resin in the molded body is 10% by weight or more because the initial fluidity becomes higher.
In addition, it is preferable that the molded body has a hollow cylindrical shape because adhesion of microorganisms is improved.
Moreover, since the fluidity | liquidity improves that the specific gravity of the said molded object is 0.8-1.2 g / cm < ³ >, it is preferable.
In addition, when 100 ml of an apparent volume of the microorganism-immobilized carrier is added to 1 L of a liquid having a solid content of 1000 mg / L and aerated at a flow rate of 1 L / min, the microorganism-immobilized carrier is within 5 hours from the start of aeration. If 80% or more of the water circulates and flows in the liquid, it is preferable because the start-up of the wastewater treatment apparatus starts quickly.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below, but the present invention is not construed as being limited thereto.
[0012]
Examples of the thermoplastic resin used in the present invention include, but are not limited to, polypropylene, polyethylene, polyvinyl chloride, ethylene-vinyl acetate copolymer resin, polystyrene, and the like. These thermoplastic resins can be used alone or in combination of two or more, and polypropylene, polyethylene and the like are particularly preferable.
[0013]
It is preferable to use an acid-denatured thermoplastic resin together with the aforementioned thermoplastic resin, since the fluidity of the carrier is further improved. Examples of the acid-modifying thermoplastic resin include propylene-maleic anhydride copolymer (for example, Mitsui Chemicals, trade name Admer, Sanyo Kasei Co., Ltd., trade name Umex, Mitsubishi Chemical Corporation, trade name) Modic), ethylene-methacrylic acid copolymer (ionomer resin, for example, Mitsui DuPont Polychemical Co., Ltd., trade name Himiran), methyl methacrylate-methacrylic acid copolymer (Mitsubishi Rayon Co., Ltd., trade name Acrypet) ) Etc. The acid-modified thermoplastic resin can be used alone or in combination of two or more.
Although the content of the acid-modified polymer depends on the amount of acid modification, it is preferably 10% by weight or more in order to give sufficient hydrophilicity, and the carrier can be obtained with only the acid-modified thermoplastic resin.
[0014]
The molded body used in the present invention may be obtained by molding the above-described resin composition by a well-known method that has been conventionally used. For example, it can be easily manufactured using an extruder, and can be manufactured using special equipment or post-processing. Can also be manufactured at low cost.
At the time of molding, the shape is not necessarily limited and can be a columnar shape, a cylindrical shape, a spherical shape, a cubic shape, or the like. A hollow cylindrical shape is preferable because adhesion of microorganisms is improved.
[0015]
Other components include calcium carbonate, talc, zeolite, barium sulfate, titanium oxide, potassium titanate, aluminum hydroxide, and other specific gravity adjusting materials, azodicarbonamide (ADCA), dinitrosopenta for making porous. Methylenetetramine (DPT), a blowing agent such as carbonic acid, a foaming aid, and further suitable additives may be included.
[0016]
The specific gravity of the molded body used in the present invention is preferably in the range of 0.8 to 1.2 g / cm ³ . Furthermore, from the viewpoint of fluidity in water, a value closer to 1.00 is more desirable. By adjusting the molded body to the above specific gravity, a suitable fluidity can be obtained when a carrier produced using the molded body is used for a fluidized bed.
[0017]
The fluidity of the carrier can be improved by acid-treating the molded body described above with an acid of 0.1 to 5 N. When the concentration of the acid used is less than 0.1 N, the initial fluidity of the carrier is equivalent to that in the case of no treatment, and the effect of the acid treatment is not recognized.
On the other hand, when treated with an acid with a concentration exceeding 5N, the resin surface is likely to erode and dissolve, which may cause problems in durability. In addition, care must be taken during handling. It is not preferable because it is dangerous.
[0018]
The type of acid to be used is not necessarily limited, and sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, acetic acid, and the like can be used. Among them, hydrochloric acid is preferable because it is inexpensive, has a high treatment effect, and is excellent in handleability.
[0019]
The treatment conditions are not particularly limited as long as the surface of the molded body comes into contact with an acid, but it is preferable to immerse the molded body in an acid solution because it can be easily treated. The temperature for immersion is not particularly limited, and the treatment may be performed at room temperature. The immersion time is preferably 0.1 to 10 hours, and more preferably 0.5 to 5 hours, taking into account the effect of improving the fluidity and the productivity.
In the immersion treatment, it is preferable to stir the liquid because the treatment efficiency is improved.
[0020]
As an evaluation of the fluidity of the microorganism-immobilized carrier, 100 ml of an apparent volume of the microorganism-immobilized carrier is added to 1 L of a liquid having a solid content of 1000 mg / L and aerated at a flow rate of 1 L / min. be able to. In this test, it is preferable that 80% of the microorganism-immobilized carrier circulates in the liquid within 5 hours from the start of aeration. In this fluidity test, the carrier that flows in a short time flows quickly even in an actual apparatus, for example, a biological wastewater treatment apparatus.
The solid content in this fluidity test refers to a substance containing a group of microorganisms capable of metabolizing and decomposing organic components in water, such as activated sludge. Desired. Those that do not have the ability to decompose organic components in water, such as inorganic substances such as sand grains and metal powders, are not included in the solid content in this fluidity test.
[0021]
Hereinafter, embodiments of the present invention will be described in detail with specific examples and comparative examples.
[0022]
1. Manufacturing method of molded body Resin and calcium carbonate are mixed using a biaxial co-directional extruder, molded into pellets, azodicarbonamide is added as a foaming agent, and extrusion molding is performed using a single screw extruder. A porous hollow cylindrical molded body having a diameter of 5 mm, an inner diameter of 3.5 mm, and a length of 5 mm was obtained.
The weight ratio of resin: calcium carbonate: foaming agent was 75: 24: 1.
[0023]
2. Acid treatment The above-mentioned molded body was immersed in an acid solution at 25 ° C. for 2 hours with stirring.
[0024]
3. Fluidity test Using the water treatment apparatus shown in FIG. 1, sludge having an MLSS concentration of 1000 mg / L and a carrier having an apparent volume of 100 ml were added to a 1 liter tank. Then, while aeration of air at 1 L / min, the artificial drainage was used as raw water, and the load was adjusted to 0.4 kg-COD / m3 · day, and the time until the carrier flowed was observed.
[0025]
<Example 1>
Polypropylene was used as the resin, and 3N hydrochloric acid was used as the acid. As a result of the fluidity test, it took 4 hours for 80% of the carrier to flow, and 6 hours for all the carriers to flow.
[0026]
<Example 2>
Propylene-maleic anhydride copolymer was used as the resin, and 3N hydrochloric acid was used as the acid. As a result of the fluidity test, it took 2 hours for 80% of the carrier to flow, and 3 hours for all the carriers to flow.
[0027]
<Example 3>
Ethylene-methacrylic acid copolymer was used as the resin, and 3N hydrochloric acid was used as the acid. As a result of the fluidity test, it took 2 hours for 80% of the carrier to flow, and 5 hours for all the carriers to flow.
[0028]
<Example 4>
Polypropylene was used as the resin, and 1N hydrochloric acid was used as the acid. As a result of the fluidity test, it took 4 hours for 80% of the carrier to flow, and 6 hours for all the carriers to flow.
[0029]
<Comparative Example 1>
Polypropylene was used as the resin, and acid treatment was not performed. As a result of the fluidity test, the time required for 80% of the carrier to flow was 36 hours, and the time required for all the carriers to flow was 48 hours.
[0030]
<Comparative example 2>
Propylene-maleic anhydride copolymer was used as the resin, and no acid treatment was performed. As a result of the fluidity test, the time required for 80% of the carrier to flow was 8 hours, and the time required for all the carriers to flow was 12 hours.
[0031]
<Comparative Example 3>
An ethylene-methacrylic acid copolymer was used as the resin, and no acid treatment was performed. As a result of the fluidity test, it took 8 hours for 80% of the carrier to flow, and 12 hours for all the carriers to flow.
[0032]
As can be seen from the above Examples and Comparative Examples, the fluidity of the carrier could be improved by acid-treating the resin molding.
[0033]
【The invention's effect】
According to the present invention, a carrier having good fluidity and excellent durability can be obtained simply, inexpensively and safely by treating a thermoplastic resin with an acid of 0.1 to 5 N. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing a water treatment apparatus used in Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Water treatment apparatus 11 Screen 12 Carrier 13 Current plate 14 Aeration pipe

Claims (5)

A microorganism-immobilized carrier having improved fluidity obtained by treating a molded article containing an acid-modified thermoplastic resin and calcium carbonate with 0.1 N to 5 N hydrochloric acid.   The microorganism-immobilized carrier according to claim 1, wherein the molded body is immersed in hydrochloric acid for 0.1 to 10 hours.   The microorganism-immobilized carrier according to claim 1 or 2, wherein the acid-modified thermoplastic resin contains a propylene-maleic anhydride copolymer.   The microorganism-immobilized carrier according to claim 1 or 2, wherein the acid-modified thermoplastic resin contains an ethylene-methacrylic acid copolymer (ionomer resin). Production of a microorganism-immobilized carrier with improved fluidity obtained by treating a molded body containing one or more kinds of resins selected from acid-modified thermoplastic resins and calcium carbonate with 0.1 N to 5 N hydrochloric acid. Method.

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